This application relates to discrete electrical resistors for television cathode ray tubes (CRTs) and in preferred forms to resistors supported on television CRT electron guns for arc suppression, voltage division or the like. Particularizing further, this invention relates to improved structure for terminating such electrical resistors.
Discrete resistors have been used on television CRT electron guns for a number of purposes, including arc suppression and voltage division. It has been found that a discrete electrical resistor for use in voltage division or arc suppression preferably takes an elongate form in order to minimize high voltage breakdown (in high voltage applications), to make possible the use of more practical resistor materials, to minimize heat generation within the resistor, and to maximize the stability of the resistor.
Problems associated with the use of discrete resistors for the named applications are those of how to mount and make electrical connection thereto. The mechanical integrity of the resistor support must be of high caliber to withstand mechanical jarring of the gun or containing tube. The mechanical support must be capable of withstanding handling during manufacture and assembly and the hostile conditions encountered during fabrication of a cathode ray tube.
The electrical connections made at the ends of the resistor must be sound and of low resistance. Such connections must not degrade during the processes encountered during fabrication of the gun and the containing cathode ray tube. The electrical connecting structure must not be such as to generate field concentrations on the terminal which might promote high voltage breakdown across the resistor or between the resistor and adjacent tube elements, nor otherwise be a factor leading to failure or degeneration of the performance or reliability of the gun or containing tube.
Yet another very important consideration is that the resistor terminating structure and the method by which the terminations are made be economical.
The prior art contains a number of disclosures of discrete electrical resistors for use in television CRTs, and in particular resistors which are mounted on television CRT guns. However these disclosures are for the most part schematic, and avoid the very real problems associated with the terminating of the resistors in a way which is practical and cost effective.
For example, U.S. Pat. No. 3,882,348-Paridaens shows an arc suppression resistor of the hollow cylinder type through which the electron beams are passed. At one end a sleeve 16 is welded to a plate 15 connected to the anodes of the electron guns. The sleeve is slid over the end of the cylindrical resistor and welded to a contact strip 21 with connection strips 24 and 25.
The Paridaens termination structure is not believed to be commercially feasible for a number of reasons. The integrity of the mechanical and electrical connection would be of questionable quality unless solder or some other similar connecting intermediary material were used. However, at the high temperatures encountered during tube fabrication, the solder would melt and escape. Further, the problems of the solder vaporizing and contaminating the gun cathodes is very real and rules out the use of this material. No suitable material to serve the solder function is known.
Gallaro et al, U.S. Pat. No. 3,295,008 discloses an arc suppression resistor which is interposed in a snubber spring on the anode of a cathode ray tube electron gun (see FIG. 4). Gallaro et al. surrounds his bulk mode resistor 57 with a ceramic or glass enclosure. Electrical contact is apparently made by extending the snubber spring components into the bulk mode material. This approach would be totally unsuitable for applications wherein a surface resistive coating is employed.
Still another approach is disclosed in British Pat. No. 1,448,223. That patent shows a cylindrical insulative core on which is disposed a helical resistive strip. Conductive end caps terminate the resistor. This approach suffers from the same drawbacks as the Paridaens approach.
U.S. Pat. No. 3,932,786-Campbell discloses a discrete voltage division resistor in the nature of a resistive strip printed on a ceramic substrate. The substrate is mounted on a glass pillar of the conventional type which supports the electrodes of an electron gun in spaced relationship. The Campbell resistor is terminated by conductors (54 and 56) which interconnect the ends of the resistor to appropriate electrodes in the gun. This approach would appear to have utility only where the glass pillar is used to support the resistor. The electrical integrity of the Campbell connections is not known.
It is known to terminate an electrical component by wrapping a conductive wire around an end thereof so as to make a terminal. However, such an approach to terminating an electrical resistor would not be useful in the applications contemplated for this invention for a number of reasons. The resultant coil would be biased to open, possibly degrading the mechanical and/or electrical interconnection. Further, wrapping process would be quite apt to destroy or damage the fragile elongate resistors to which this invention is applied.